The present invention relates generally to a signal transmission line connector, a signal transmission line, a signal transmission cable and a data processing system and more particularly to a signal transmission line connector, a signal transmission line, a signal transmission cable and a data processing system for use in a transmission line network such as an Ethernet network.
When designing an Ethernet network, the design must conform to the ANSI IEEE Standard 802.3 1993, which regulates the design including that of the transmission circuit for each network adapter so as to assure correct operation of the network.
To provide a lap-top personal computer (PC) with Ethernet functions using a mini-PCI type network card of, for example, the Type III model, therefore, the PC includes a transmission line so as to correspond to the Ethernet.
However, in case the lap-top PC must be provided with a port replication function at an RJ45 port at such an extended unit side used as, for example, a docking station and/or in case a mechanically efficient transmission line is disposed in the lap-top PC, a transmission line connector other than the RJ45 connector must be used unavoidably on the transmission line network, although the use of such a nonstandard connector should be avoided originally.
When such a nonstandard transmission line connector is used, a return loss occurs at the connection area due to impedance mismatching. Consequently, a stationary wave is generated, thereby attenuating the signal. This disables the subject data communication, resulting in a communication error.
In such a case, a transmission line connector that satisfies the characteristics required for the Ethernet Standard should be used. Otherwise, it would be difficult to develop a new transmission line connector that agrees to the design requirement each time a system is developed when the number of processes and the cost are taken into consideration.
Japanese Published Unexamined Patent Application No. 9-51209, the contents of which are incorporated herein by reference, discloses a technique for preventing such impedance mismatching by changing both the permittivity of the substrate material and the width of the transmission line pattern. This technique, which unavoidably changes the permittivity of the substrate material gives rise to an increase in manufacturing cost.
Under such circumstances, it is an object of the present invention to provide a signal transmission line connector, a signal transmission line, and a substrate that can prevent the whole subject transmission line network from degradation of the transmission characteristics even when the network uses a transmission line connector whose characteristic impedance differs from that required for the transmission lines.
In order to attain the above object, the transmission line connector of the present invention enables a signal transmission line to be connected to a terminal area in an transition region. The transmission line is formed at a predetermined width so as to transmit a signal and the terminal area is formed at a specific width differently from the predetermined width so as to input/output a signal to be transmitted by the signal transmission line. The transition region is formed around the terminal area so that the predetermined width of the signal transmission line is changed gradually to the specific width of the terminal area in the transition region as the line goes towards the terminal area.
And, a plurality of such signal transmission lines are also formed on, for example, a flexible cable at a predetermined width therebetween and those transmission lines are used, for example, for communications among computers via a network. At an end or at a middle point of each of those transmission lines is formed a terminal area used to input/output a signal. This terminal area can be formed not only on the flexible cable, but also another type of substrate such as a printed circuit board. The terminal area has a specific width, which is different from that of the signal transmission line. Consequently, the impedance differs between the signal transmission line and the terminal area.
Consequently, in the present invention, the transition region is formed so that the predetermined width of the signal transmission line is changed gradually to the specific width of the terminal area therein as the line goes towards the terminal area and the transmission line is connected to the terminal area therein. And, because the width of the signal transmission line is changed gradually around the terminal area, the impedance around the terminal area can be prevented from an abrupt change even when the impedance differs between the signal transmission line and the terminal area. Consequently, a return loss to be expected around the terminal area can be reduced, thereby the attenuation of the signal can be prevented so as to assure normal communications.
The length of the transition region, that is, the length of the section in which the width of the signal transmission line is changed gradually, can be decided as follows, for example. At first, an impedance is found from an equalizing circuit of the signal transmission line system including the signal transmission line and the terminal area, then the area of the transition region, which is equivalent to the impedance, is found. This area can be found in accordance with the required impedance from the inductance and capacitance characteristics of the material of the signal transmission line. When the area of the transition region is decided, the length of the transition region can be found easily from the area, the predetermined width of the signal transmission line, and the specific width of the terminal area.